Articulated dump trucks comprise a front part (tractor) including an internal combustion engine and drivers cab; and a rear part (trailer) including a pivotable body for holding the material to be moved; the front and rear parts being pivotable relative to one another. It is known, in such vehicles, to pass the exhaust gases from the engine through an exhaust pipe system across the pivot between the front and rear parts to suitable ducts in the body, the heat generated by the exhaust gases aiding the removal of sticky or frozen material from the body, when the body is pivoted to dump the material. Articulated dump trucks are susceptible, on occasion, to rolling over, usually with the rear part rolling over whilst the front part remains upright. On such an occasion, the exhaust pipe system is usually extensively damaged between the front and rear parts of the vehicle. This has the disadvantage of leaving the vehicle unusable until it is repaired, and leaving the vehicle requiring maintenance, both of which add considerably to the running costs of the vehicle. It may also require a stock of replacement components to be stored. One solution to this problem has been to include a long length of flexible tube in the exhaust pipe system between the front part and the rear part of the vehicle. This arrangement has the disadvantage of the problem raised by positioning and securing of the long flexible tube during normal operation of the vehicle.